Fan clutch apparatus and methods

ABSTRACT

Some embodiments of a fan clutch system may drive an output member to rotate at a first speed when opposing friction clutch surfaces are engaged and to rotate at a second, slower speed when the friction clutch surfaces are shifted to a disengaged position. In particular embodiments, the multi-speed clutch system may employ an eddy current drive system that is arranged axially rearward of the friction clutch surfaces while the fan blade device is mounted in a position that is axially forward of the of the friction clutch surfaces.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the priority benefit of U.S. ProvisionalApplication for Patent Ser. No. 61/297,531, entitled “Fan ClutchApparatus and Methods,” filed on Jan. 22, 2010 which is herebyincorporated by reference for all purposes.

BACKGROUND

Vehicle transmission systems, cooling systems, and braking systems mayemploy clutches or like devices to selectively transmit rotationalforces from a drive source to an output member. For example, somecooling systems employ fan clutch devices that control the outputrotation of engine cooling fans. Such a fan clutch can be driven by adrive pulley that rotates in response to the vehicle engine.

In general, the clutch can be operated to engage (or disengage) opposingclutch surfaces, which rotationally interconnect (or rotationallydisconnect) the drive pulley and the output member. In an examplerelated to fan clutches, when the clutch surfaces shifted to the engagedposition, the output member (carrying fan blades) is driven to rotatealong with the drive pulley. However, when the clutch surfaces areshifted to the disengaged position, the output member is no longerdirectly urged by the drive pulley.

SUMMARY

Some embodiments of a clutch system may drive an output member to rotateat a first speed when the clutch surfaces are engaged and to rotate at asecond speed when the clutch surfaces are shifted to a disengagedposition. In particular embodiments, the multi-speed clutch system mayemploy an eddy current drive system that is arranged axially rearward ofthe clutch surfaces to cause the output member to rotate even when theclutch surfaces are disengaged. Such an arrangement of the eddy currentdrive components can provide ample space for heat dissipation structuresalong the periphery of the eddy current drive system, especially in someembodiments in which the cooling fins of the eddy current drive systemextend radially outward for exposure to the air flow path from a fanblade device mounted to a forward face of the output member.

The multi-speed clutch device can be useful, for example, to control therotation of a cooling fan in a vehicle cooling system, such as a coolingsystem in semi-trucks, buses, vocational equipment (e.g., garbagetrucks), or construction equipment vehicles. In such circumstances, thecooling fan can be driven to rotate at a first speed due to rotationalinterconnection with a drive pulley when the clutch surfaces are engagedand to rotate at a second speed even when the clutch surfaces aredisengaged. Thus, the clutch system facilitates the flow of cooling airboth when the vehicle cooling system activates the fan (e.g., by causingthe clutch surfaces to engage) and when the vehicle cooling systemdeactivates the fan (e.g., by causing the clutch surfaces to disengage).Accordingly, the vehicle engine can be maintained below high-temperaturethreshold for greater periods of time, thereby reducing the number oftimes and the time duration that the fan clutch device must be engagedto rotate the fan blades at the first, full speed. As a result, the fuelefficiency of the vehicle may be substantially increased due to thereduction in load upon the engine caused by the full speed rotation ofthe fan blade device.

These and other embodiments described herein may be configured toprovide one or more of the following advantages. First, some embodimentsof the clutch devices described herein can drive an output member torotate at a first speed when the clutch surfaces are engaged and torotate at a second speed when the clutch surfaces are shifted to adisengaged position. In particular, the clutch device can employ an eddycurrent drive system that urges the output member of the clutch deviceto rotate at the second speed (which may be slower than the firstspeed).

Second, the eddy current drive components (e.g., permanent magnets andan opposing eddy current ring) can be positioned axially rearward of thefriction drive surfaces while the fan blade device is positioned axiallyforward of the friction drive surfaces. Such an arrangement can provideadditional space for cooling fins along a periphery of one or more eddycurrent drive components without interfering with the operation of thefan blade device. Further, such an arrangement provides an operable eddycurrent drive system without substantially increasing the size of theclutch device in the region that is radially outward of the frictionclutch components.

Third, some embodiments of the clutch device can be implemented with acooling fan so as to provide different levels of air flow output fromthe cooling fan. For example, the fan clutch device can be useful forcooling systems in some vehicles that operate with extended periods ofidle, such as semi-trucks, buses, vocational equipment (e.g., garbagetrucks), or construction equipment vehicles. In such circumstances, thefan clutch device facilitates the flow of cooling air both when thevehicle cooling system activates the fan (e.g., by causing the clutchsurfaces to engage) and when the vehicle cooling system deactivates thefan (e.g., by causing the clutch surfaces to disengage). As describedbelow, periods of increased noise from the vehicle cooling fan rotatingat the first (higher) speed can be reduced or eliminated due to the flowof cooling air from the fan rotating at the second (slower) speed.

Fourth, the eddy current drive system of the clutch device may includepermanent magnets that are arranged adjacent to the electricallyconductive ring in a manner that provides consistent operation andefficient dissipation of heat from the eddy current drive components.For example, in some embodiments, the conductive ring can be arrangedradially outward from the permanent magnets so that the heat generatedby the production of eddy currents in the conductive ring can bedissipated radially outward through a plurality of cooling fins. Also,the conductive ring (and the cooling fins attached thereto) can rotateat the first (higher) speed with the drive pulley during operation,thereby causing the cooling fins to generate increased air movement thatenhances the heat dissipation from the conductive ring.

Fifth, the conductive ring of the eddy current drive system can beformed from a generally nonmagnetic material such as aluminum or thelike. In such circumstances, the ring is not necessarily attracted orrepelled by the magnets during assembly, which reduces the complexity ofaligning and assembling components of the clutch device. Furthermore, inthose embodiments in which the conductive ring is formed from anonmagnetic material such as aluminum or the like, the conductive ringmay have a lower mass (e.g., compared to some magnetic materials such assteel) and more efficient heat dissipation properties.

The details of one or more embodiments of the invention are set forth inthe accompanying drawings and the description below. Other features,objects, and advantages of the invention will be apparent from thedescription and drawings, and from the claims.

DESCRIPTION OF DRAWINGS

FIG. 1A is a perspective exploded view of a fan clutch system includinga clutch device coupled between a fan blade device and a drive member,in accordance with some embodiments.

FIG. 1B is a side exploded view of the fan clutch system of FIG. 1A.

FIG. 1C is a cross-sectional side view of the clutch device of theclutch system of FIG. 1A.

FIG. 2 is a cross-sectional side view of an alternative clutch devicefor use in a fan clutch system, in accordance with some embodiments.

FIG. 3 is a cross-sectional side view of another alternative clutchdevice for use in a fan clutch system, in accordance with someembodiments.

Like reference symbols in the various drawings indicate like elements.

DETAILED DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS

Referring to FIGS. 1A, 1B, and 1C, some embodiments of a clutch system10 can include a clutch device 100 that couples a fan blade device 180to a drive pulley 190. The drive pulley 190 may be driven to rotateabout a central axis 105 via a belt connection 192 with a component of avehicle engine. As such, the clutch system may be assembled into avehicle, such as near the front of a semi-truck or near the rear of apassenger bus.

As described in more detail below, some embodiments of the clutch device100 can include an input member 110 and an output member 120 (FIG. 1C).Turning to FIG. 1B, the input member 110 of FIG. 1C (not illustrated)can be mounted to the drive pulley 190 via mounting bolts 194 so thatthe input member 110 is rotationally coupled with the drive pulley 190.Returning to FIG. 1C, the input member 110 can be selectively coupled tothe output member 120 by a frictional drive system 150 so as torotatingly drive the output member 120 at a first speed. Further, aneddy current drive system 170 can provide rotational output at a secondspeed (when the clutch friction surfaces are disengaged). In suchcircumstances, the clutch device 100 can be controlled to providerotational control, for example, to the fan blade device 180 (asillustrated in FIGS. 1A and 1B) of an engine cooling system in thevehicle. Accordingly, as shown in FIG. 1C, the fan blade device 180 (notillustrated) can be operated at the first speed when a friction ring152, affixed to the output member 120 at an output surface 122 viamounted bolts (not shown), is axially shifted to engage an opposingfriction surface 112 to thereby rotate with the drive pulley 190 orother drive source. Furthermore, the fan blade device 180 can beoperated at the second speed due to the operation of the eddy currentdrive system 170 when the friction ring 152 is axially shifted away fromthe opposing friction surface 112 to disengage the frictional drivesystem 150.

Such a multi-speed clutch system can be effective to provide differentlevels of airflow output from the fan blade device 180. For example,some vehicles may operate with extended periods of idle, such assemi-trucks, buses, vocational equipment (e.g., garbage trucks), orconstruction equipment vehicles, so the cooling system may periodicallyactivate the clutch device 100 to start rotation of fan blade device 180to cool the engine. The high-speed rotation of the fan blades in thesevehicles might be noticeably loud to both passengers (inside the vehiclecabin) and pedestrians (outside the vehicle cabin), especially when thevehicle is running at idle. However, the clutch device 100 describedherein can be implemented within the vehicle cooling systems so that thefan blades are rotated at a second speed even when the cooling systemhas not activated the clutch device 100 to frictionally engage thefriction ring 152 with the friction surface 112. The second speed of thefan blade device 180 may be less than the first speed, and thus thenoise from the fan blade device 180 may be reduced. Furthermore, theclutch device 100 facilitates the flow of cooling air both when thevehicle cooling controller activates the fan (e.g., by causing theclutch friction surfaces to engage) and when the vehicle coolingcontroller deactivates the fan (e.g., by causing the clutch frictionsurfaces to disengage). Thus, the vehicle's engine temperature can bemaintained below a threshold level for a greater period of time, whichreduces the frequency that clutch device 100 must be activated by thecooling system to rotate the cooling fan at the first (and perhapslouder) speed.

Briefly, in operation, the clutch system 10 may include a drive sourcesuch as the drive pulley 190 that is rotated at a first speed due toconnection with an engine output shaft via a belt, chain, gear, or thelike. (Note that the fan blade device 180 and the drive pulley 190 areremoved from FIG. 1C for purposes of illustration, but are depicted inFIGS. 1A-1B.) The clutch device 100, as illustrated in FIG. 1C, includesthe input member 110 that is directly or indirectly mounted to the drivepulley 190 so as to rotate at the first speed with the drive pulley 190.In this embodiment, the input member 110 includes two or more mountingholes 114 to receive mounting bolts (not shown) that couple the inputmember 110 to the drive pulley 190. The clutch device 100 also includesthe output member 120 that can be actuated to engage or disengage withthe input member 110. For example, the output member 120 can axiallyshift in response to movement of a piston 124 that is adjustablerelative to the input member 110. The axial movement of the outputmember 120 can cause the friction ring 152 to axially shift intofrictional engagement or disengagement with the friction surface 112 onthe input member 110. When the friction ring 152 is shifted to theengaged position, the output member 120 is urged to rotate at the firstspeed with the input member 110 and the drive pulley 190. Because thefan blade device 180 is mounted to a front face of the output member 120(e.g., via two or more mounting studs 166 or other removable couplingmechanism), the fan blade device 180 likewise rotates at the first speedwith the input member 110 and the drive pulley 190 when the frictionring 152 (couple to the output member 120) frictionally engages theinput member 110.

The friction ring 152 and the friction surface 112, in someimplementations, are generally defined by a frusto-conical frictioninterface in which the radius of the frusto-conical friction interfaceincreases as the frusto-conical friction interface extends away from thedrive pulley 190. Conversely, the radius of the frusto-conical frictioninterface may increase as the frusto-conical friction interface extendstowards the drive pulley 190. The friction ring 152 may comprise ametallic, ceramic or other material that is capable of providingfrictional engagement and is capable of dissipating heat generated atthe frictional interface. For example, some embodiments of the frictionring 152 may comprise a material having a static coefficient or frictionin the range of approximately 0.2 to approximately 0.6 and, inparticular embodiments, may comprise a material having a staticcoefficient of friction in the range of approximately 0.4 toapproximately 0.5. The shape and orientation of the frusto-conicalfriction ring 152 and the friction surface 112 may provide the clutchdevice 100 with a conical wedging action. This conical wedging actionmay improve the engagement friction, thereby providing enhanced torquetransfer capabilities. In other implementations, the friction ring 152and the friction surface 112 are defined by a substantially flatfriction interface.

Still referring to FIGS. 1A-1C, the clutch device 100 also includes theeddy current drive system 170 that urges the output member 120 to rotateat a second speed different from the first speed when the friction ring152 is shifted to the disengaged position due to axial adjustment of theoutput member 120. In this embodiment, the eddy current drive system 170includes a set of two or more permanent magnets 172 arranged along amagnet mounting plate 174 that is attached to the output member 120. Insome implementations, the permanent magnets 172 are magnetically coupledto the magnet mounting plate 174. For example, the magnet mounting plate174 may include a steel portion that provides magnetic coupling for thepermanent magnets 172. In other implementations, the permanent magnets172 are mechanically coupled to the magnet mounting plate 174, in someexamples, through the use of screws, bolts, welding, plastic, or a highstrength epoxy material.

The eddy current drive system 170 further includes an eddy current ring178 formed substantially of an electrically conductive material (e.g.,aluminum in this embodiment), which is spaced apart from the permanentmagnets 172 by a small air gap. The eddy current ring 178 can be mountedto the input member 110 via a set of mounting bolts (not shown). Forexample, the eddy current ring 178 may have a central portion that abutswith a radial face of the input member 110 such that mounting holes (notshown) in the eddy current ring 178 align with the mounting holes 114 ofthe input member 110. Thus, when the drive pulley is bolted to the inputmember 110, the eddy current ring 178 is sandwiched therebetween androtates with the drive pulley 190 and the input member 110. Accordingly,when the friction ring 152 is shifted to disengage the friction surface112 so that the output member 120 rotates relative to the input member110, the permanent magnets 172 (coupled with the output member 120) canmove relative to the eddy current ring 178 (coupled to the input member110). Such relative movement may cause eddy currents to be generated inthe eddy current ring 178, which produces a force between the eddycurrent ring 178 and the permanent magnets 172. Because the eddy currentring 178 is rotated at the first speed along with the input member 110,the force between the permanent magnets 172 and the eddy current ring178 causes the magnet mounting plate 174 to thereby drive the outputmember 120 to rotate at the second speed (which may be less than thefirst speed).

Referring again to FIGS. 1A-1B, in the illustrated embodiment the drivepulley 190 can be rotatably coupled to a support shaft by one or morebearings (not shown). This support shaft may include a central channelthat is used to deliver pressurized fluid to the clutch device 100. Forexample, as illustrated in FIG. 1C, the clutch device 100 may include acentral shaft 126 having a coupling end 130 for insertion into a matingregion of the support shaft of the drive pulley 190. This coupling end130 is abutted between a rear bearing 128 b and the support shaft of thedrive pulley 190 and provides a generally airtight seal so thatpressurized fluid delivered through the support shaft of the drivepulley 190 is advanced through a fluid channel 132 of the clutch device100 and into a fluid receiving chamber 140 at least partially defined bythe piston 124. As such, when the clutch device 100 is mounted to thedrive pulley 190, the coupling end 130 is pressed into a central channelof the support shaft of the drive pulley 190 so as to provide fluidcommunication with a fluid supply reservoir

As shown in FIG. 1C, in some embodiments, the coupling end 130 mayinclude a dual seal arrangement so as to provide enhanced sealingfeatures at the interface between the clutch device 100 and the supportshaft of the drive pulley 190. In particular, the coupling end 130 mayinclude a first sealing ring 138 comprising a first polymer material.The coupling end 130 may also include a second sealing ring 139comprising a second polymer material that is significantly stiffer(e.g., a higher durometer rating) than the first polymer material of thefirst sealing ring 138. Such an arrangement of the first and secondsealing rings 138 and 139 along the coupling end 130 of the clutchdevice 100 can reduce the likelihood of clutch failure during operationof the vehicle. For example, the clutch device 100 can continue tooperate in a satisfactory manner even if one of the two sealing rings138 and 139 ruptures or leaks after extended wear. The fluid transmittedto or withdrawn from the fluid-receiving fluid receiving chamber 140 ofthe clutch device 100 may be any suitable liquid or gas. Such fluids maybe received, for example, from a pneumatic air supply system or ahydraulic oil supply system.

The fluid-receiving fluid receiving chamber 140 may be at leastpartially defined by a front face of the piston 124 and a nose cap 142.The nose cap 142 can be mounted to a forward end of the central shaft126, and thus remains generally fixed relative to the stationary centralshaft 126. As such, when pressurized air is delivered into thefluid-receiving fluid receiving chamber 140, the piston 124 is adjusteda small distance in an axially rearward direction relative to the nosecap 142 and the central shaft 126. A seal ring 168 and a dust wiper 169can be arranged proximate to an outer periphery of the piston 124 so asto seal the single leak path at the periphery.

Still referring to FIG. 1C, the rear face of the piston abuts with aforward bearing 128 a, which is axially adjustable with the piston 124.The forward bearing 128 a is mounted to a first spring-engaging member125 a, which slidably shifts along the central shaft 126 relative to asecond spring-engaging member 125 b. A spring 125 c is arranged betweenthe first and second spring engaging members 125 a-b and biases theforward bearing 128 a and the piston 124 toward the nose cap 142 at thefront of the clutch device 100. Thus, when the pressurized fluid isdelivered into the fluid-receiving fluid receiving chamber 140, thepiston 124, the forward bearing 128 a, and the first spring-engagingmember 125 a are adjusted a small distance in an axially rearwarddirection against the bias force of the spring 125 c. When thepressurized fluid is evacuated from the fluid-receiving fluid receivingchamber 140, the spring 125 c urges the piston 124, the forward bearing128 a, and the first spring-engaging member 125 a to return to anaxially forward position. As described below, this reciprocating motioncauses the friction ring 152 to adjust into and out of engagement withthe input member 110. In some implementations, two or more springs canbe used in the place of the spring 125 c.

The second spring-engaging member 125 b abuts with an inner race of therear bearing 128 b, which also abuts on an opposite side with a collar127 of the central shaft 126. Accordingly, the rear bearing 128 bremains generally axially stationary with the central shaft 126 whilethe forward bearing 128 a can axially adjust relative to the centralshaft 126 (as previously described). The input member 110 is mounted onthe rear bearing 128 so that the input member 110 is rotatable relativeto the central shaft 126 but remains axially stationary relative to thecentral shaft 126. The output member 120 is mounted on the forwardbearing 128 a so that the output member 120 is rotatable relative to thecentral shaft 126 and is axially adjustable relative to the centralshaft 126 when the piston 124 and forward bearing 128 a are axiallyshifted.

Still referring to FIG. 1C, in this embodiment, the output member 120 ofthe clutch device 100 includes a central hub region 160 and afan-mounting region 164. When the fluid-receiving fluid receivingchamber 140 is pressurized, the piston 124 is urged against the force ofthe spring 125 c, causing the forward bearing 128 a to adjust in anaxially rearward direction. The output member 120, which is mounted onthe forward bearing 128 a, axially adjusts in the rearward directionalong with the forward bearing 128 a. As shown in FIG. 1C, this rearwardaxial adjustment of the output member 120 creates a narrow gap betweenthe friction ring 152 and the friction surface 112, thereby permittingthe output member 120 to rotate relative to the input member 110. Whenthe pressurized fluid is evacuated from the fluid-receiving fluidreceiving chamber 140, the piston 124, the forward bearing 128 a, andthe output member 120 are urged by the spring 125 c in an axiallyforward direction, which causes the friction ring 152 to press againstthe opposing friction surface 112 and couple the output member 120 tothe input member 110.

The fan-mounting region 164 of the output member 120 is configured toreceive a fan blade device 180 (as shown in FIGS. 1A and 1B) or anotheroutput instrument to be rotated. In particular, the fan-mounting region164 may include two or more mounting studs 166 that are configured toreceive the fan blade device 180. As shown in FIGS. 1A-1B, the fan bladedevice 180 can be configured to fit over the central hub region 160 ofthe output member 120 and engage with a front face of the fan-mountingregion 164. The fan blade device 180 can include a plurality of fanblade structures 182 that are arranged to generate air flow, forexample, as part of a vehicle's engine cooling system. The fan bladestructures 182 can be angled, tapered, curved, or otherwise configuredto direct the output of air flow. In the illustrated embodiment of FIG.1A, the fan blade device 180 includes two or more mounting holes 184that are configured to receive the mounting studs 166 extending from theclutch device 100. In alternative embodiments, the output member 120 ofthe clutch device 100 may be configured to receive an output instrumentother than a fan blade device 180. For example, the fan-mounting region164 may be configured to connect with other components that are to beselectively rotated, such as output shafts, gears, brake systems, andthe like. Accordingly, in these embodiments, the output member 120serves as both the component that shifts friction ring 152 to engage ordisengage the input member 110 and the component that receives an outputinstrument (such as the fan blade device 180 in FIGS. 1A-1B).

In various implementations, the eddy current ring 178 can include anumber of cooling fins 179. In the example of the clutch device 100, thecooling fins 179 extend radially outward from the outer periphery of theeddy current ring 178. For example, the cooling fins 179 can be formedof the same material as the eddy current ring 178 (e.g., machined into asingle piece of metal). The cooling fins 179, for example, may extendsubstantially from a point radially outward of the outer position of thepermanent magnets 172. In other implementations, the cooling fins 179are coupled to the eddy current ring 178. In other embodiments, coolingfins may additionally or alternatively be formed in or otherwise coupledto the magnet mounting plate 174. In some embodiments, the cooling fins179 may be formed in such an arrangement to provide effectivedissipation of heat that may be generated in the eddy current ring 178when the input member 110 and output member 120 are not frictionallyengaged. For example, the described radial arrangement may place thecooling fins 179 in a flow of air generated by rotation of the fanblades 182. In the embodiment illustrated in FIGS. 1A-1C, the permanentmagnets 172 and the eddy current ring 178 are arranged axially rearwardof the engagement surface and the friction surface 112. In someembodiments, the cooling fins 179 may be formed in such an arrangementto provide effective dissipation of heat that may be generated in theeddy current ring 178 when the input member 110 and output member 120are not frictionally engaged. For example, according to the exampleshown in FIG. 1C, the cooling fins 179 can rotate at the first speedwith the drive pulley to provide substantially similar heat dissipationof the eddy current ring 178 during the engaged and disengaged stages ofoperation of the clutch device 100.

In some embodiments, this arrangement can provide sufficient space forthe eddy drive system 170 components and the cooling fins 179 withouthaving to increase the outer radius of the clutch device 100 in theregion that is directly radially outward from an engagement surface 154and the friction surface 112. For example, by not increasing the outerradius of the clutch device 100, the clutch device 100 may beimplemented to retrofit a friction-only (e.g., engaged or disengaged)clutch system with one that provides two speed operation (e.g., eddycoupled or frictionally coupled). A conversion kit may include themagnet mounting plate 174, the eddy current ring 178, the cooling fins179, the set of permanent magnets 172, and appropriate tools andfasteners to couple the components of the eddy drive system 170 to thefriction-only clutch system. In some implementations, the eddy currentring 178 and the magnet mounting plate 174 may be designed to bedetachably coupled to an input member and an output member of thefriction-only clutch system, respectively, and to be able to rotaterelatively during the disengagement of the friction-only clutch system.The set of permanent magnets 172 may be magnetically coupled to themagnet mounting plate 174. Accordingly, the relative rotation betweenthe permanent magnets 172 and the eddy current ring 178 may generate aneddy current in the eddy current ring 178, in which the resultingmagnetic force urges the permanent magnets 172, and therefore the outputmember of the friction-only clutch system, to rotate at the second speedduring the disengagement of the friction-only clutch system.

In some implementations of the clutch device 100, when the fan bladedevice 180 spins during engagement, it can produce a thrust componentsubstantially in the same direction as the spring force. This force canincrease the overall frictional force between the input and outputmembers 110, 120, which can increase the torque of the output member120. In selective embodiments, the thrust component from the rotation ofthe fan blade device during the engagement of the clutch device 100 candepend on the number of fan blades, diameter of the fan blade device,and the first speed. Example number of fan blades may be 5, 7, 9, 11, or13. The diameter of the fan blade device may range from about 20 inchesto about 30 inches, about 25 inches to about 35 inches, or about 30inches to about 40 inches. The diameter of the fan blade device may beabout 36 inches, for example. Increasing the number of fan blades, thediameter of the fan blade device, or both, can lead to higher thrustcomponent. Also, during the engagement of the clutch device, the firstspeed of the fan blade device can be substantially similar to rotationalspeed of the drive pulley 190, which may vary according to therotational speed of the engine output shaft. Increasing the first speedcan increase the thrust component.

Referring now to FIG. 2, some embodiments of the clutch system 10 mayinclude the fan blade device 180 that is coupled to a clutch device 200that is different from the clutch device 100 illustrated in FIG. 1C. Forexample, the clutch device 200 may include an eddy current drive system270 that is configured differently from the eddy current drive system170 described in connection with FIG. 1C.

As shown in FIG. 2, the clutch device 200 may include the input member110, the output member 120, and the friction ring 152 havingsubstantially the same configuration as the previously describedembodiments depicted in FIGS. 1A-C. Also, similar to the previouslydescribed embodiments, the clutch device 200 depicted in FIG. 2 mayinclude the central shaft 126 having the coupling end 130, the first andsecond spring-engaging members 125 a-b. the spring 125 c, the forwardbearing 128 a, the rear bearing 128 b, the piston 124, the nose cap 142,and the mounting studs 166 to receive the fan blade device 180.

Accordingly, the friction drive system 150 of the clutch device 200(FIG. 2) may operate in the manner as described in connection with theembodiments previously described in connection with FIGS. 1A-C. As shownin FIG. 2, when the fluid-receiving fluid receiving chamber 140 ispressurized, the piston 124 is urged against the force of the spring 125c, causing the forward bearing 128 a to adjust in an axially rearwarddirection. The output member 120, which is mounted on the forwardbearing 128 a, axially adjusts in the rearward direction along with theforward bearing 128 a. As shown in FIG. 2, this rearward axialadjustment of the output member 120 creates a narrow gap between thefriction ring 152 and the friction surface 112, thereby permitting theoutput member 120 to rotate relative to the input member 110. When thepressurized fluid is evacuated from the fluid-receiving fluid receivingchamber 140, the piston 124, the forward bearing 128 a, and the outputmember are urged by the spring 125 c in an axially forward direction,which causes the friction ring 152 to press against the opposingfriction surface 112 and couple the output member 120 to the inputmember 110.

The clutch device 200 depicted in FIG. 2 includes the eddy current drivesystem 270 that is different from the eddy current drive system 170depicted in FIG. 1C. For example, the eddy current drive system 270 caninclude a set of permanent magnets 272 that are spaced apart from aneddy current ring 278 so as to define a circumferential gap 202therebetween. In this embodiment, the permanent magnets 272 are affixedabout the inner periphery of a magnet ring 204 by bolts (not shown),which is in turn assembled to the output member 120. As such, thepermanent magnets 272 are coupled with the output member 120, and theoutput member 120 rotates when the permanent magnets 272 are driven torotate. The eddy current ring 278 is mounted to an extension plate 214that is mounted to the input member 110 (via bolts through the mountingholes 114). As such, the eddy current ring 278 rotates with the inputmember 110, which is driven to rotate drive the drive pulley 190 (asillustrated in relation to FIG. 1A).

As previously described, when the output member 120 is not frictionallyengaged to the input member 110 (via the friction ring 152), the outputmember 120 is not driven to rotate at the same speed as the input member110. Due to this relative rotation between the input member 110 and theoutput member 120, the eddy current ring 278 is driven to rotaterelative to the set of permanent magnets 272. In some implementations,eddy currents may be induced in the eddy current ring 278 as it rotatesrelative to the permanent magnets 272, thereby urging the permanentmagnets 272 (and magnet ring 204) to rotate at a second, slower speed.The magnet ring 204 is affixed to the output member 120, so it urges theoutput member 120 (and the fan blade device 180 mounted thereto) torotate at the second, slower speed under the influence of the eddycurrent drive system 270 when the input member 110 and the output member120 are not frictionally engaged.

In the embodiment illustrated in FIG. 2, the permanent magnets 272 andthe eddy current ring 278 are arranged axially rearward of theengagement surface 154 and the friction surface 112. This arrangementcan provide sufficient space for the eddy drive system 270 componentsand extending cooling fins 279 without having to increase the outerradius of the clutch device 200 in the region that is directly radiallyoutward from the engagement surface 154 and the friction surface 112.For example, because the outer radius of the clutch device 200 is notsignificantly increased outward from the engagement surface 154 and thefriction surface 112, the clutch device 200 may be implemented toretrofit a friction-only (e.g., engaged or disengaged) clutch systemwith one that provides two speed operation (e.g., eddy coupled orfrictionally coupled).

Still referring to FIG. 2, the permanent magnets 272 can be carried bythe magnet ring 204 so that the permanent magnets 272 are oriented toface radially inward along one or more inner circumferential surfaces ofthe magnet ring 204. In such circumstances, the eddy current ring 278may be arranged radially inward of the permanent magnets 272 so that anouter circumferential surface of the eddy current ring 278 is adjacentto the permanent magnets 272 with the circumferential air gap 202therebetween. The air gap 202 can be configured to be large enough so asto avoid frictional contact between the permanent magnets 272 and theeddy current ring 278. Also, the circumferential air gap 202 can beconfigured to be small enough so that relative movement between the eddycurrent ring 278 and the magnet ring 204 induces the formation of eddycurrents in the conductive material of the magnet ring 204. For example,in this embodiment, the circumferential air gap 202 between thepermanent magnets 272 and the eddy current ring 278 is about 0.125inches or less, about 0.005 inches to about 0.100 inches, and preferablyabout 0.020 inches. The eddy currents are formed in the eddy currentring 278 in response to relative motion of the permanent magnets 272because a moving magnetic field intersects a conductor (e.g., theconductive eddy current ring 278). Accordingly, the eddy current drivesystem 270 can create a force that urges the magnet ring 204, and thusthe output member 120, to rotate at a second speed that is differentfrom the first rotational speed of the input member 110 and the drivepulley 190. Further, the size of the air gap 202 between the permanentmagnets 272 and the eddy current ring 278 is not dependent upon theaxial position of the piston 124 or the output member 120. The air gap202 remains generally constant even when the piston 124 adjusts to causethe output member 120 to shift from the frictionally engaged conditionto the frictionally disengaged condition.

Still referring to FIG. 2, the inner periphery of the eddy current ring278 includes a number of cooling fins 279 extending radially inward. Insome embodiments, the cooling fins 279 may be formed in such anarrangement to provide effective dissipation of heat that may begenerated in the eddy current ring 278 when the input member 110 andoutput member 120 are not frictionally engaged. In some embodiments,this arrangement can provide sufficient space for the eddy drive system270 components and the cooling fins 279 without having to increase theouter radius of the clutch device 200 in the region that is directlyradially outward from the engagement surface 154 and the frictionsurface 112. For example, by not increasing the outer radius of theclutch device 100, the clutch device 100 may be implemented to retrofita friction-only (e.g., engaged or disengaged) clutch system with onethat provides two speed operation (e.g., eddy coupled or frictionallycoupled).

In some implementations, the inwardly radial placement of the coolingfins 279 may at least partly shield the cooling fins from damage byexternal objects, or vice versa. For example, the described inwardlyradial arrangement may protect the cooling fins 279 from being damagedby road debris, or other materials that may inadvertently come intocontact with the clutch device 200. In another example, the describedinwardly radial arrangement may substantially keep the cooling fins 279away from encountering and damaging or injuring objects that mayinadvertently come into contact with the clutch device 200 while it isrotating (e.g., loose wires, dangling hoses, a mechanic's fingers).

Referring now to FIG. 3, some embodiments of the clutch system 10 mayinclude the fan blade device 180 that is coupled to a clutch device 300that is different from the clutch devices 100 and 200 illustrated inFIGS. 1C and 2, respectively. For example, the clutch device 300 mayinclude an eddy current drive system 370 that is configured differentlyfrom the eddy current drive systems 170 and 270 described in connectionwith FIGS. 1C and 2, respectively.

Referring to FIG. 3, the clutch device 300 may include the input member110, the output member 120, and the friction ring 152 havingsubstantially the same configuration as the previously describedembodiments. Also, similar to previously described embodiments, theclutch device 300 depicted in FIG. 3 may include the central shaft 126having the coupling end 130, the first and second spring-engagingmembers 125 a-b, the spring 125 c, the forward bearing 128 a, the rearbearing 128 b, the piston 124, the nose cap 142, and the mounting studs166 to receive the fan blade device 180.

Accordingly, the friction drive system 150 of the clutch device 300 mayoperate in the manner as described in connection with the previousembodiments. As shown in FIG. 3, when the fluid-receiving fluidreceiving chamber 140 is pressurized, the piston 124 is urged againstthe force of the spring 125 c, causing the forward bearing 128 a toadjust in an axially rearward direction. The output member 120, which ismounted on the forward bearing 128 a, axially adjusts in the rearwarddirection along with the forward bearing 128 a. As shown in FIG. 3, thisrearward axial adjustment of the output member 120 creates a narrow gapbetween the friction ring 152 and the friction surface 112, therebypermitting the output member 120 to rotate relative to the input member110. When the pressurized fluid is evacuated from the fluid-receivingfluid receiving chamber 140, the piston 124, the forward bearing 128 a,and the output member are urged by the spring 125 c in an axiallyforward direction, which causes the friction ring 152 to press againstthe opposing friction surface 112 and couple the output member 120 tothe input member 110 (so that the output member 120 rotates with theinput member 110 at the speed of the drive pulley 190 (shown in FIGS.1A-B)).

The clutch device 300 depicted in FIG. 3 may include the eddy currentdrive system 370 in which a set of permanent magnets 372 and an eddycurrent ring 378 are arranged to define a narrow circumferential air gap302 therebetween. In this embodiment, the permanent magnets 372 areaffixed about the outer periphery of a magnet-mounting plate 314 (bybolts 306), which can be mounted to the input member 110 (via boltsthrough the mounting holes 114). As such, the permanent magnets 372rotate with the input member 110, which is driven to rotate the drivepulley 190 (FIG. 1A). In this implementation, an eddy current ring 378is assembled to the output member 120 so that the eddy current ring 378is arranged radially outward of the set of permanent magnets 372. Assuch, the eddy current ring 378 is coupled with the output member 120,and the output member 120 rotates when the eddy current ring 378 isdriven to rotate.

As previously described, when the output member 120 is not frictionallyengaged to the input member 110 (via the friction ring 152), the outputmember 120 is not driven to rotate at the same speed as the input member110. Due to this relative rotation between the input member 110 and theoutput member 120, the eddy current ring 378 is driven to rotaterelative to the set of permanent magnets 372. In some implementations,eddy currents may be induced in the eddy current ring 378 as it rotatesrelative to the permanent magnets 372, thereby urging the eddy currentring 378 to rotate at a second, slower speed while the permanent magnets372 rotate substantially at the drive speed of the drive pulley 190(e.g., the rotational speed of the input member 110). The eddy currentring 378 is affixed to the output member 120, so that it urges theoutput member 120 (and the fan blade device 180 mounted thereto) torotate at the second, slower speed under the influence of the eddycurrent drive system 370 when the input member 110 and the output member120 are not frictionally engaged.

In the embodiment illustrated in FIG. 3, the eddy current drive system370 (including the permanent magnets 372 and the eddy current ring 378)is arranged axially rearward of the frusto-conical engagement surface154 and the friction surface 112. This arrangement can providesufficient space for the eddy drive system 370 components and a set ofcooling fins 379 without having to increase the outer radius of theclutch device 300 in the region that is directly radially outward fromthe engagement surface 154 and the friction surface 112. For example,because the outer radius of the clutch device 300 is not significantlyincreased outward from the engagement surface 154 and the frictionsurface 112, the clutch device 300 may be implemented to retrofit afriction-only (e.g., engaged or disengaged) clutch system with one thatprovides two speed operation (e.g., eddy coupled or frictionallycoupled).

Still referring to FIG. 3, the permanent magnets 372 can be carried bythe magnet-mounting plate 314 so that the permanent magnets 372 areoriented to face radially outward along at least one outercircumferential surface of the magnet-mounting plate 314. In suchcircumstances, the eddy current ring 378 may be arranged radiallyoutward of the permanent magnets 372 so that an inner circumferentialsurface of the eddy current ring 378 is adjacent to the permanentmagnets 372 with a small circumferential air gap 302 therebetween. Thecircumferential air gap 302 can be configured to be large enough so asto avoid frictional contact between the permanent magnets 372 and theeddy current ring 378. Also, the circumferential air gap 302 can beconfigured to be small enough so that relative movement between thepermanent magnets 372 and the eddy current ring 378 induces theformation of eddy currents in the conductive material of the eddycurrent ring 378. For example, in this embodiment, the circumferentialair gap 302 between the permanent magnets 372 and the eddy current ring378 is about 0.125 inches or less, about 0.005 inches to about 0.100inches, and about 0.020 inches. Accordingly, the eddy current drivesystem 370 can create a force that urges the eddy current ring 378, andthus the output member 120, to rotate at a second speed that isdifferent from the first rotational speed of the input member 110 andthe drive pulley 190. Further, the size of the circumferential air gap302 between the permanent magnets 372 and eddy current ring 378 is notdependent upon the axial position of the piston 124 or the output member120. The circumferential air gap 302 remains substantially constant evenwhen the piston 124 adjusts to cause the output member 120 to shift fromthe frictionally engaged condition to the frictionally disengagedcondition.

In the embodiment illustrated in FIG. 3, the outer periphery of the eddycurrent ring 378 includes a number of cooling fins 379 extending in aradially outward direction. In some implementations, each of the coolingfins 379 can extend fully around a circumference of the eddy currentring 378. Alternatively, the cooling fins 379 can be arranged in amanner similar to the cooling fins 179 depicted in FIG. 1C, or thecooling fins 379 can be formed of a single continuous spiral. In someembodiments, the cooling fins 379 may be formed in such an arrangementto provide effective dissipation of heat that may be generated in theeddy current ring 378 when the input member 110 and output member 120are not frictionally engaged. For example, the cooling fin arrangementdepicted in FIG. 3 may place the cooling fins 379 in a flow pathgenerated by rotation of the fan blades 182. In some embodiments, thisarrangement can provide sufficient space for the eddy drive system 370components and the cooling fins 379 without having to increase the outerradius of the clutch device 300 in the region that is directlycircumferentially outward from the engagement surface 154 and thefriction surface 112. For example, by not increasing the outer radius ofthe clutch device 300, the clutch device 300 may be implemented toretrofit a friction-only (e.g., engaged or disengaged) clutch systemwith one that provides two speed operation (e.g., eddy coupled orfrictionally coupled).

A number of embodiments of the invention have been described.Nevertheless, it will be understood that various modifications may bemade without departing from the spirit and scope of the invention.Accordingly, other embodiments are within the scope of the followingclaims.

What is claimed is:
 1. A fan clutch device to be mounted to a drivepulley, the fan clutch device comprising: an input member that isremovably mountable with the drive pulley such that the input memberrotates with the drive pulley; an output member that is adjustable in anaxial direction between first and second positions relative to the inputmember; a clutch ring arranged between the input member and the outputmember, the clutch ring including a first friction surface that engagesan opposing friction surface when the output member is in the firstposition such that the output member rotates at a first speed with theinput member; a piston which is adjustable in an axial directionrelative to the input member; a central shaft passing through first andsecond bearings, the output member being mounted on the first bearingand the input member being mounted on the second bearing; first andsecond spring-engaging members which are disposed between the first andsecond bearings; a spring arranged between the first and secondspring-engaging members which biases the piston, the first bearing, andthe first spring-engaging member toward a nose cap at a front of the fanclutch device; and an eddy current drive system that urges the outputmember to rotate at a second speed different from the first speed whenthe output member is in the second position, the eddy current drivesystem including: permanent magnets circumferentially disposed on aring, the ring being attached to one of the output member and the inputmember, and an electrically conductive ring coupled to the other of theoutput member and the input member on an axial face thereof, wherein thepermanent magnets and the electrically conductive ring are positionedaxially rearward of the clutch ring, wherein a fluid-receiving fluidchamber is defined in part by the piston and the nose cap such that whenpressurized air enters the fluid-receiving chamber, the piston, thefirst bearing, and the first spring-engaging member are adjusted in anaxially rearward direction against a bias force of the spring therebyurging the output member into the second position.
 2. The device ofclaim 1, wherein the output member comprises a front face to receive afan blade device in an output position that is axially forward of theclutch ring.
 3. The device of claim 1, wherein a circumferential air gapis defined between the permanent magnets and the electrically conductivering of the eddy current drive system.
 4. The device of claim 1, whereinthe friction surface of the clutch ring comprises a frusto-conicalfriction surface.
 5. The fan clutch device of claim 1, wherein theelectrically conductive ring is coupled to the input member while thepermanent magnets are coupled to the output member.
 6. The fan clutchdevice of claim 5, wherein the electrically conductive ring includesradially extending cooling fins to dissipate heat.
 7. The fan clutchdevice of claim 1, wherein the electrically conductive ring is comprisedof a generally nonmagnetic material, and the eddy current drive systemsubstantially includes no magnetic material positioned to oppose thepermanent magnets.
 8. A clutch device comprising: an input member thatis removably mountable with a drive member such that the input memberrotates with the drive member; an output member including: a hub that isselectively movable relative to the input member, and a pistonadjustable in an axial direction relative to the input member, thepiston being adjustable between first and second positions; a firstdrive system that urges the output member to rotate at a first speedwhen the piston is adjusted to the first position; and an eddy currentdrive system that urges the output member to rotate at a second speeddifferent from the first speed when the piston is adjusted to the secondposition, the eddy current drive system including: permanent magnetscircumferentially disposed on a ring, the ring being attached to one ofthe output member and the input member, and an electrically conductivering coupled to the other of the output member and the input member onan axial face thereof, wherein the permanent magnets and theelectrically conductive ring are positioned axially rearward of thefirst drive system, wherein the output member is mounted on a firstbearing and the input member is mounted on a second bearing, wherein thefirst drive system includes: first and second spring-engaging memberswhich are disposed between the first and second bearings, and a springarranged between the first and second spring-engaging members whichbiases the piston, the first bearing, and the first spring-engagingmember toward a nose cap at a front of the fan clutch so as to adjustthe piston in the first position, and wherein a fluid-receiving fluidchamber is defined in part by the piston and the nose cap such that whenpressurized air enters the fluid-receiving chamber, the piston, thefirst bearing, and the first spring-engaging member are adjusted in anaxially rearward direction against a bias force of the spring therebyurging the output member into the second position.
 9. The clutch deviceof claim 8, wherein the first drive system includes a clutch ringarranged between the input member and the output member, the clutch ringincluding a first friction surface that engages an opposing frictionsurface when the piston is in the first position such that the outputmember rotates at the first speed, the first speed being substantiallyequivalent to an input speed of the input member.
 10. The clutch deviceof claim 9, wherein the clutch ring comprises a frusto-conical clutchring that provides a conical wedging action when engaged with theopposing friction surface.
 11. The clutch device of claim 8, wherein theoutput member is removably coupled to a fan blade device, wherein thefan blade device is coupled to the clutch device in an output positionthat is axially forward of the first drive system.
 12. The clutch deviceof claim 8, wherein a circumferential air gap is defined between thepermanent magnets and the electrically conductive ring.
 13. The clutchdevice of claim 8, wherein the permanent magnets are coupled to theoutput member, and the electrically conductive ring is coupled to theinput member, the electrically conductive ring including radiallyextending cooling fins to dissipate heat.
 14. The clutch device of claim8, wherein the electrically conductive ring is comprised of a generallynonferrous material, and the eddy current drive system substantiallyincludes no ferrous material positioned to oppose the permanent magnets.15. A conversion kit for converting an on-off fan clutch device to atwo-speed fan clutch device, the on-off fan clutch device comprising aninput portion that removably engages with a drive member, an outputmember that removably engages with a rotational device, and a clutchring arranged between the input portion and the output member, theclutch ring including a first friction surface that engages an opposingfriction surface when the output member is in a first position such thatthe output member rotates at a first rotational speed with the inputportion, the conversion kit comprising: an eddy current drive systemthat urges the output member to rotate at a second rotational speeddifferent from the first rotational speed when the output member is in asecond position, the eddy current drive system including: permanentmagnets circumferentially disposed on a ring, the ring being attached toone of the output member and the input portion, and an electricallyconductive ring coupled to the other of the output member and the inputportion on an axial face thereof, wherein the permanent magnets and theelectrically conductive ring are positioned axially rearward of theclutch ring when the conversion kit is coupled to the on-off fan clutchdevice, wherein the rotational device, when engaged with the outputmember, is positioned axially forward of the clutch ring, wherein theoutput member is mounted on a first bearing of the on-off fan clutchdevice and the input member is mounted on a second bearing of the on-offfan clutch device, and wherein the on-off fan clutch device includes: apiston which is adjustable in an axial direction relative to the inputmember, a central shaft passing through first and second bearings, firstand second spring-engaging members which are disposed between the firstand second bearings, and a spring arranged between the first and secondspring-engaging members which biases the piston, the first bearing, andthe first spring-engaging member toward a nose cap at a front of the fanclutch device to urge the output member into the first position.
 16. Theconversion kit of claim 15, wherein a circumferential air gap is definedbetween the permanent magnets and the electrically conductive ring. 17.The conversion kit of claim 15, wherein the permanent magnets arecoupled to the output member, and the electrically conductive ring iscoupled to the input portion, the electrically conductive ring includingradially extending cooling fins to dissipate heat.
 18. The conversionkit of claim 15, wherein the electrically conductive ring is comprisedof a generally nonferrous material, and the eddy current drive systemsubstantially includes no ferrous material positioned to oppose thepermanent magnets.
 19. The conversion kit of claim 15, furthercomprising a magnet mounting plate including ferrous material, whereinthe permanent magnets are coupled to the magnet mounting plate throughmagnetic force.
 20. The conversion kit of claim 19, wherein the magnetmounting plate is attached to the output member using two or more boltsand the electrically conductive ring abuts with a radial face of theinput portion and is attached to the input portion using two or morebolts.